Infrared Luminescence of Fe³⁺ in CuGaS₂ and CuAlS₂

Abstract

A sharp luminescence line due to the crystal-field transition (⁴T₁–⁶A₁) of Fe³⁺ in the tetrahedral symmetry is observed for the first time in iron-doped I–III–VI₂ chalcopyrite type compounds, CuGaS₂ and CuAlS₂. The peak energy is 4,942 cm⁻¹ and 5,804 cm⁻¹ respectively. These values are rather small as compared to those in many ferric oxides in which the excitation energy of ⁴T₁ in octahedral symmetry is observed around 10,000 cm⁻¹.
The Zeeman effect is also observed and is explained quantitatively by the use of the ligand field theory: We find that g_⊥ of the lowest excited state is zero and the spin-orbit parameter 18 cm⁻¹.